Sleeve Cap Ease Calculator
A sleeve cap has to be longer than the armhole to cover the round of the shoulder. On a 46 cm armhole at 8%, the cap measures 49.7 cm and 3.7 cm has to disappear without a single pleat. That 3.7 cm is not spread evenly: most of it goes into the upper third between the front and back notches, and none into the 3–4 cm just above the underarm seam, where the curve is nearly straight and there is nowhere to put it.
Your numbers
Sleeve cap length
49.7cm
Ease to distribute
3.7cm
Formula
Sleeve cap length = Armhole circumference × (1 + Sleeve cap ease ÷ 100), Ease to distribute = Sleeve cap length − Armhole circumference
The fabric sets the percentage. Wool and flannel will shrink 5 cm away under the iron, while coated cotton, taffeta and leather pucker past about 1 cm, and knits take none at all (0–2%). A flat-set shirt sleeve wants only 2–3%; a tailored jacket, with a pad behind it, takes 8–12%. Measure the armhole along the seam line with the tape standing on edge — running it inside the allowance reads about 2 cm short.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Armhole circumference (cm)The armhole measured right round its seam line; inside the allowance reads short. | 46 | 1 and up |
| Sleeve cap ease (%)How much longer the cap is than the armhole — only as much as the fabric can take. | 8 | 0 ~ 20 |
Step by step
Quick reference table
Results when only Armhole circumference (cm) changes and everything else stays put.
| Armhole circumference (cm) | Sleeve cap length (cm) | Ease to distribute (cm) |
|---|---|---|
| 23 | 24.8 | 1.8 |
| 34.5 | 37.3 | 2.8 |
| 46 | 49.7 | 3.7 |
| 69 | 74.5 | 5.5 |
| 92 | 99.4 | 7.4 |
What each result means
| Result | At default values |
|---|---|
| Sleeve cap length (cm)Length of the sleeve cap curve, longer than the armhole by the ease. | 49.7 |
| Ease to distribute (cm)Length to work in without pleats, concentrated between the notches. | 3.7 |
Common mistakes
The fabric sets the percentage. Wool and flannel will shrink 5 cm away under the iron, while coated cotton, taffeta and leather pucker past about 1 cm, and knits take none at all (0–2%). A flat-set shirt sleeve wants only 2–3%; a tailored jacket, with a pad behind it, takes 8–12%. Measure the armhole along the seam line with the tape standing on edge — running it inside the allowance reads about 2 cm short.
Glossary
- Armhole circumference
- The armhole measured right round its seam line; inside the allowance reads short.
- Sleeve cap ease
- How much longer the cap is than the armhole — only as much as the fabric can take.
- Sleeve cap length
- Length of the sleeve cap curve, longer than the armhole by the ease.
- Ease to distribute
- Length to work in without pleats, concentrated between the notches.
Frequently asked questions
Q. How is Sleeve Cap Ease Calculator calculated?
Sleeve cap length = Armhole circumference × (1 + Sleeve cap ease ÷ 100), Ease to distribute = Sleeve cap length − Armhole circumference — A sleeve cap has to be longer than the armhole to cover the round of the shoulder. On a 46 cm armhole at 8%, the cap measures 49.7 cm and 3.7 cm has to disappear without a single pleat. That 3.7 cm is not spread evenly: most of it goes into the upper third between the front and back notches, and none into the 3–4 cm just above the underarm seam, where the curve is nearly straight and there is nowhere to put it.
Q. Can you walk through an example?
With Armhole circumference 46cm, Sleeve cap ease 8%, the answer is Sleeve cap length 49.7cm.
Q. What do I need to enter?
Enter Armhole circumference, Sleeve cap ease. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Armhole circumference (cm) moves the answer to Armhole circumference (cm) 23 → Sleeve cap length (cm) 24.8 and Armhole circumference (cm) 92 → Sleeve cap length (cm) 99.4. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
The fabric sets the percentage. Wool and flannel will shrink 5 cm away under the iron, while coated cotton, taffeta and leather pucker past about 1 cm, and knits take none at all (0–2%). A flat-set shirt sleeve wants only 2–3%; a tailored jacket, with a pad behind it, takes 8–12%. Measure the armhole along the seam line with the tape standing on edge — running it inside the allowance reads about 2 cm short.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.